Volatile compounds flavor contribution

Flavor is one of the major characteristics that restricts the use of legume flours and proteins in foods. Processing of soybeans, peas and other legumes often results in a wide variety of volatile compounds that contribute flavor notes, such as grassy, beany and rancid flavors. Many of the objectionable flavors come from oxidative deterioration of the unsaturated lipids. The lipoxygenase-catalyzed conversion of unsaturated fatty acids to hydroperoxides, followed by their degradation to volatile and non-volatile compounds, has been identified as one of the important sources of flavor and aroma components of fruits and vegetables. An enzyme-active system, such as raw pea flour, may have most of the necessary enzymes to produce short chain carbonyl compounds. 

Roasting cocoa beans results in the production of volatile and non-volatile compounds which contribute to the total flavor complex. 5-Methyl-2-phenyl-2-hexenal, which exhibited a deep bitter persistant cocoa note, was reported in the volatile fraction (53). It was postulated to be the result of aldol condensation of phenylacetaldehyde and isovaleraldehyde with the subsequent loss of water. The two aldehydes were the principal products of Strecker degradation products of phenylalanine and leucine, respectively. Non-volatiles contained diketopiperazines (dipeptide anhydride) which interact with theobromine and develop the typical bitterness of cocoa (54). Theobromine has a relatively stable metallic bitterness, but cocoa bitterness is rapidly noticed and disappears quickly. 

Chemical compounds having odor and taste number in the thousands. In 1969 a description of the odor characteristics of more than three thousand chemical compounds used in the flavor and perfume industries were described (41). The Hst of volatile compounds found in food that may contribute to odor and taste is even larger (42), and the Hst of all possible flavor compounds, including those that have yet to be synthesized, is greater than a thousand. Many different compounds have the same flavor character or quaUty, differing perhaps in their relative intensity but indistinguishable in the type of flavor they ehcit. The exact number of different flavor quaUties is not known, but it appears to be much less than the total number of compounds with flavor. 

The central question that I want to approach here is the possible relationship between flavor preferences and nutritional value. There are a lot of data to work with. More than 70(X) volatile flavor substances have been identilied in foods and beverages. The situation may not be quite as complex as this would suggest. While it is true that any single fruit or vegetable may synthesize a few hundred volatile compounds, only a modest subset of these will contribute to its flavor profile. So the task is to sort out what these are, identify their sources, and link, where possible, these sources to nutritional value. Studies with the tomato provide a great example. The bottom line is Virtually all of the major tomato volatiles can be linked to compounds providing health benefits to humans. ... 

Homstein and Crowe 18) and others (79-27) suggested that, while the fat portion of muscle foods from different species contributes to the unique flavor that characterizes the meat from these species, the lean portion of meat contributes to the basic meaty flavor thought to be identical in beef, pork, and lamb. The major differences in flavor between pork and lamb result from differences in a number of short chain unsaturated fatty acids that are not present in beef. Even though more than 600 volatile compounds have been identified from cooked beef, not one single compound has been identified to date that can be attributed to the aroma of "cooked beef." Therefore, a thorough understanding of the effect of storage on beef flavor and on lipid volatile production would be helpful to maintain or expand that portion of the beef market. 

It should be kept in mind that most analytical instruments, such as gas chromatographs and mass spectrometers, do not discriminate between volatile compounds that do or do not possess odor activity. Some form of sensory analysis must be conducted in order to select which volatile compounds contribute to the flavor of the foods. Gas chromatography-olfactometry (GC/O) is an important tool to accomplish that task. 

Raw meat has little desirable flavor, but each type of meat has a characteristic flavor due to the animal species and the temperature and type of cooking. Both water-soluble and lipid-soluble fractions contribute to meat flavor and the water-soluble components include precursors which upon heating are converted to volatile compounds described as "meaty."... 

Lipid-derived volatile compounds play an important role in the flavor of foods. These compounds contribute to the characteristic notes of many dairy flavors, but are also responsible for many off-flavors. Parliament and McGorrin (2000) reviewed those volatile compounds important in milk, cream, butter, cultured creams and cheese. The pathways involved in the degradation of milk fat have also been reviewed by McSweeney and Sousa (2000) and compounds include FFAs, methyl ketones, lactones, esters, aldehydes, primary and secondary alcohols, hydroxyacids, hydroperoxides and ketoacids. 

Food flavor is a very important parameter influencing perceived quality. The volatile compounds contributing to the aroma of foods possess different chemical characteristics, such as boiling points and solubilities and the sensory properties of food cannot be understood only from the knowledge of aroma composition. This can be explained by interactions between flavor compounds and major constituents in food such as fat, proteins and carbohydrates (1). A number of different interactions has been proposed to explain the association of flavor compound with other food components. This includes reversible Van der Waals interactions and hydrogen bonds, hydrophobic interactions. The understanding of interactions of flavor with food is becoming important for the formulation of new foods or to... 

The knowledge of the composition of volatile compounds in food has greatly increased during the past decade. Many studies continue to report the identity and the concentration of volatile compounds in food matrices. However concentration alone appears insufScient to explain flavor properties of food. The lack of our knowledge concerning the influence of non-volatile constituents of food on the perception of aroma has to be filled by studies such as those presented in this paper. Data on interactions between aroma and matrix in wine are scarce compared with other food matrices studied. Flavor-matrix interactions in wine have generally been obtained in model systems and with instrumental experiments. However it is possible to develop some hypotheses on the possible sensory contribution of some non-volatile compounds of wine on overall aroma. 

TABLE 8. The Amounts of Volatile Flavor Contributing Compounds from Lards of Different Treatments (47). 

Van den Ouweland, G. A.M. Components contributing to beef flavor. Volatile compounds produced by the reaction of 4-hydroxy-5-methyl-3(2//)-fiiranone and its thio analog with hydrogen sulfide. J. Agric. Food Chem. 1975, 23, 501-505. 

While a large number of volatile compounds contribute to the flavor of raspberries, most are present at less than 10 ppm. 

Aldehydes are by far the most numerous compounds identified as dry-cured ham odorants, with different odors (green, rancid, toasted) and thresholds in air ranging from 0.09 to 480 ng/L (Table 1). Most of them were identified in the first works focused on dry-cured ham volatile compounds (7,2). Aldehydes are essential for meat flavor (70), but large quantities in meat and meat products have been related to lipid oxidation and deterioration (77). The effect of several quality factors has been researched and it was found that the rearing system of pigs (S) and ripening conditions (7) influence on the contribution to odor and the content of some aldehydes. 

Yaylayan, V. A. and Keyhani, A. 1996. Pyrolysis/GC/MS analysis of non-volatile flavor precursors Amadori compounds. In Contribution of low- and non-volatile materials to the flavor of foods, ed. P. Winterhalter, C.-T. Ho, and A. M. Spanier, 13-26. Carol Stream, IL Allured Publishing. 

Some aldehydes have been identified in green coffee by Guyot et al. (1983). These authors mention the presence in green coffee of 2,4-dimethylpentanal (C.15), a compound which has not been identified in the roasted beans. Some volatile unsaturated aldehydes contribute to the typical green coffee odor and may impact the cultivar-related flavor or off-flavor characteristics in corresponding roasted coffee. 

Karahdian C., Josephson D.B. and Lindsay R.C. (1985b) Volatile compounds from Penicillium sp. contributing musty-earthy notes to Brie and Camembert cheese flavors. J. Agric. Food. Chem., 33, 339-343. 

Several volatile constituents have been reported in fenugreek (2), mainly terpenes and fatty acids. However, no systematic work has yet been published on compounds that contribute to the characteristic aroma of fenugreek. 3-Hydroxy-4,5-Uiinclhyl-2(5//)-furanone (sotolone) was suggested as an important volatile constituent of fenugreek due to its seasoning-like flavor note (J, /)... 

---